Test: Cell - Structure & Functions (June 17) - NEET MCQ

1. Centriole: There are two main functions of centrioles

• Cell division :The main function of the centriole is to help with cell division in animal cells.  The centrioles help in the formation of the spindle fibres that separate the chromosomes during cell division (mitosis).
• Ciliogenesis :The second function of centrioles that we will focus on is ciliogenesis. Ciliogenesis is simply the formation of cilia and flagella on the surface of cells.  Cilia and flagella help the cell move. 

2. Chlorophyll molecules are arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts.
3. A crista is a fold in the inner membrane of a mitochondrion.
4. Ribosomes comprise a complex macromolecular machine, found within all living cells, that serves as the site of biological protein synthesis  (translation). Ribosomes link amino acids together in the order specified by messenger RNA(mRNA) molecules.

Hence, the correct option is A
NCERT Reference: Topics “8.5.9 Centrosome and Centrioles”, “8.5.5 Plastids”, “8.5.4 Mitochondria” and “8.5.6 Ribosomes” of chapter 8 of NCERT

• When the centromere is situated in the middle of two equal arms of chromosomes, the chromosome is called Metacentric.
• When the centromere is present slightly away from the middle, it is called sub-metacentric chromosome.
• When the centromere is present very close to one end of the chromosome, it is known acrocentric chromosome.
• When the centromere is present at terminal position, chromosome is refers as telocentric.

• Mitochondria are miniature biochemical factories where food stuffs or respiratory substrates are completely oxidised to carbon dioxide and water.
• During aerobic respiration, carbohydrates are completely oxidised in mitochondria. In mitochondria, the Krebs cycle and electron transport chain occur, and ATP is generated. As a result, mitochondria are known as a cell's powerhouse.

• ATP comes out of mitochondria and helps perform various energy-requiring processes of the cell like muscle contraction, nerve impulse conduction, biosynthesis, membrane transport, cell division, movement, etc. Because of the formation of ATP, the mitochondria are called power houses of the cell.

Hence, the correct option is C
NCERT Reference: Page no. 135 of topic “8.5.4 Mitochondria” of chapter 8 of NCERT

(d) Synapsis is the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I, Zygotene of meiosis. 

(a) Meiosis is a process (discovered by German biologist, Oscar Hertwig) where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells - sperm in males, eggs in females. Crossing over is the process by which two chromosomes, exchange some distal part of their DNA. This process occurs in the Pachytene stage of Prophase I of meiosis.

(a) Synapsis → Crossing over → Terminalisation of chiasmata → Disappearance of nucleolus 

• Lysosomes are formed by the process of packaging in the Golgi apparatus.
• They are membrane-bound and possess hydrolytic enzymes which work optimally in acidic pH.
• Lysosomes bud off from the trans face to Golgi bodies.
• Precursors of lysosomal enzymes are synthesized by RER and then sent to Golgi bodies for further processing.

Hence, the correct option is A
NCERT Reference: Page no. 134 of sub-topic “8.5.3.3 Lysosomes” of chapter 8 of NCERT

• Ribosomes are the protein factory of a cell. These are non-membranous organelle which attach to the endoplasmic reticulum by transcolon.

• Lysosomes are membrane-bound vesicular structures formed by the process of packaging in the Golgi apparatus. 
• Mesosomes are a specialised differentiated form of cell membrane and is the characteristic of prokaryotes. They are essentially infoldings of cell membrane.
• The vacuole is the membrane-bound space found in the cytoplasm. It contains water, sap, excretory product and other materials not useful for the cell.

Hence, the correct option is A

NCERT Reference: Page no. 136 of topic “8.5.6 Ribosomes” of chapter 8 of NCERT

• A nuclear membrane, also known as the nuclear envelope, nucleolemma or karyotheca, is the double lipid bilayer membrane which surrounds the genetic material and nucleolus in eukaryotic cells.
• Recent developments have shown that nuclear membrane is derived from rough endoplasmic reticulum.
• During cell division, the nuclear membrane is disintegrated.
• The nuclear envelope transmembrane proteins are absorbed in the RER.
• Once the division is completed, RER reassembles the nuclear envelope.

Hence, the correct option is C

NCERT Reference: Page no. 138 of topic “8.5.10 Nucleus” of chapter 8 of NCERT

• The cell wall is the hard protective covering of all plant, fungal and some bacterial cells.
• Mycoplasma is a genus of bacteria that lack a cell wall and are surrounded by their cell membrane only.

Hence, the correct option is B

NCERT Reference: Page 128 of topic “8.4 PROKARYOTIC CELLS” of chapter 8 of NCERT

• The microtubules are found in the cytoplasmic matrix of all eukaryotic cells. They also occur in cilia, flagella, centrioles, basal bodies, and mitotic apparatus.
• Spindle fibres form the protein structure which helps in mitosis and meiosis.

• Centrioles are the two cylindrical structures of a cell organelle called centrosome.

• Cilia and flagella are fine hair-like outgrowths of the membrane.
• While peroxisomes are the microbodies.

Hence, the correct option is C

NCERT Reference: Page no. 137 of topic “8.5.9 Centrosome and Centrioles” of chapter 8 of NCERT

• The cytoskeleton is unique to eukaryotic cells. It is a dynamic three-dimensional structure that fills the cytoplasm. This structure acts as both muscle and skeleton, for movement and stability. The long fibres of the cytoskeleton are polymers of subunits. The primary types of fibres comprising the cytoskeleton are microfilaments, microtubules, and intermediate filaments.
• Microfilaments are fine, thread-like protein fibres, 3-6 nm in diameter. They are composed predominantly of a contractile protein called actin.

• Microtubules are cylindrical tubes, 20-25 nm in diameter. They are composed of subunits of the protein tubulin--these subunits are termed alpha and beta. 
• Intermediate filaments are about 10 nm diameter and provide tensile strength for the cell. Lamin is the protein present in intermediary filaments.
• Lamin is the protein present in intermediary filaments.

Hence, the correct option is B

NCERT Reference: Page no. 136 of topic “8.5.7 Cytoskeleton” of chapter 8 of NCERT

(a) The enzyme recombinase is required at Pachytene stage of meiosis. It catalyzes the exchange of short pieces of DNA between two long DNA strands, particularly the exchange of homologous regions between the paired maternal and paternal chromosomes. 

G₁, or first growth phase is followed by S phase or synthesis phase. DNA replication occurs in S phase and DNA amount doubles up i.e., a cell with 2C DNA in G, phase will now have 4C DNA. G₂, phase is second growth phase where DNA content remains 4C.

In a 1665 publication called Micrographia, experimental scientist Robert Hooke coined the term “cell” for the box-like structures he observed when viewing cork tissue through a lens.

Hence, the correct option is B